Cutting tools in the prior art, such as end mill cutting tools or rotatable milling tools, have been provided with indexable inserts to substantially increase the utility of the tool. More specifically, prior to the use of indexable inserts, the replaceable blades employed had only a single sharpened edge. To reduce manufacturing costs, an indexable insert, formed from tungsten carbide material, was developed having a plurality of sharpened cutting edges. In use, when a cutting edge beomes dull, the indexable insert is merely rotated such that a fresh sharpened edge is positioned to extend outwardly from the cutter in an active cutting position.
To maximize the number of cutting edges on a single insert, it is preferable that the insert be symmetrical in configuration to permit indexing annd mounting of the insert in a variety of orientations. Thus, the prior art inserts may be square, circular, triangular, pentagonal, hexagonal or octagonal (multi-faceted) in configuration so as to be readily indexed and mounted to expose a fresh sharpened cutting edge.
The cutter bodies which were adapted to receive the indexable inserts of the prior art are generally provided with pockets adapted to receive the inserts, which include a platform area and one or more side walls. The indexable insert is inserted in one of the pockets and is oriented such that one of the planar surfaces thereof abuts the platform surface of the pocket of the cutter body. In addition, the side walls of the pocket are adapted to abut and brace one or more of the inactive sides of the insert. By this arrangement, the side walls prevent the insert from rotating about its central axis during the use of the cutting tool. Preventing shifting or rotating of the insert during use is required such that desired axial and radial rake angle, as well as the lead angle of the cutting edge is maintained.
As can be appreciated, the tooling or machining of the insert pockets in a tool body is difficult and time consuming and thus, relatively expensive. The side walls of the pocket must be formed with relatively high structural rigidity to prevent the breakdown of the cutter during operation. In addition, the number of pockets which may be formed in a cutting tool of a given size is limited and thus, the number of inserts which may be placed around the circumference of the tool is correspondingly limited.
Accordingly, it is an object of the subject invention to provide an improved holder assembly for an indexable insert which functions to restrict the unwanted rotational movement of the insert during the operation of the cutter.
It is another object of the subject invention to provide a new and improved holder assembly for an indexable insert which eliminates the need for side walls of a receiving pocket.
It is a further object of the subject invention to provide a holder assembly for an indexable insert which will allow the mounting of two or more inserts in close proximity, since the need for the side walls of the pocket are eliminated. By this arrangement, the number of inserts which may be mounted on a tool of a given size is increased.